Forget Bluetooth device

How do I get my iPhone 12 to forget a Bluetooth device that it won’t connect to anymore? The instructions in an earlier question here about reconnecting to my Yamaha sound bar say to start by telling iPhone to forget the device. It can’t forget a device it won’t connect to.

i have tried the second suggestion of resetting the soundbar, the. Reactivating the Bluetooth on my phone and reconnecting, but that doesn’t work either.